Writing Scripts in Nashorn - Scripting in Java: Integrating with Groovy and JavaScript - page 150

You can also create regular expressions using regular expression literals. The syntax
to use a regular expression literal is:

/pattern/flags

The following are examples of creating regular expressions using the regular
expression literals:

var pattern1 = /Java/gm; // The same as new RegExp("Java", "gm")
var pattern2 = /Nashorn/; // The same as new RegExp("Nashorn")

A regular expression literal is converted to a RegExp object every time is it evaluated.
According to this rule, if two regular expression literals with the same contents appear in
the same program, they will evaluate to two different RegExp objects, as shown:

// pattern1 and pattern2 have the same contents, but they evaluate to
// different RegExp objects
var pattern1 = /Java/gm;
var pattern2 = /Java/gm;

// Prints false in both cases
print(pattern1 === pattern2);
print(/Nashoern/ === /Nashorn/);

The RegExp.prototype object contains three methods as listed in Table 4-16 .
The test() method is a specialized case of the exec() method. The toString() method
returns the string form of the regular expression. You only need to learn the exec()
method in detail.

Table 4-16. The List of Methods in the RegExp.prototype Object

Method Description

exec(string) Performs a match on string against the regular expression. Returns

an Array object containing the results of the match or null if there
was no match

test(string) Calls the exec(string) method. Returns true if the exec() method

returns not null , false otherwise. Use this method instead of the
exec() method if you care about only to know whether there is a
match

toString() Returns a string of the form /pattern/gim , where gim is the flags that

were specified when the RegExp object was created